Air-swept machines for husking, polishing or whitening cereal grains are very well known in the art and many types thereof are extant in the marketplace.
However, the machines for husking and/or polishing cereal grains extant in the prior art, generally have to be set to work in separate stages, namely, a husking stage and a polishing and/or whitening stage, and with the proviso that the husking machines which are introduced in the first stage must deliver completely husked grain to the polishing machines, because the latter are uncapable of handling unhusked grains, whereby the husking stage generally needs several steps carried out by tandems of husking machines and/or by husking machines followed by unhusked grain removing machines.
Different designs of polishing machines are also well known but, up to the present time, there are very few machines designed that may effect a complementary husking of the grain to avoid the use of unhusked grain removing machines, and only said very few machines accomplished the goal of also polishing the grain in one single step with the posthusking step, with the consequent increases in the cost of fully husking the grains and the consequent cumbersome procedure that must be used with said type of tandem husking machines and unhusked grain removing machines to deliver a fully husked grain to the polishing machines.
Among the most well known grain polishing machines are those using emery cones or emery cylinders to polish the grains by means of rubbing of the same with emery, thus producing a polished grain and flour from the rubbed portions thereof. These machines, however, are extremely bulky and heavy and their operation requires high power consumption, whereby the process carried out thereby is rather costly.
Many compact type horizontal polishing machines for grains, particularly rice, are also known, but this compact type machines use a rotor the rotation of which causes intermittent projection of the grains that therefore are accelerated or decelerated, depending on the cycle involved, whereby the treating of the grain is harsh and irregular and a large amount of breakage of said grains occurs.
On the other hand, most of the well known air-swept polishing machines for cereal grains generally have resource to a cylindrical rotor and a polygonal indented screen, because it was believed up to the present time that the use of such polygonal indented screen would increase the performance of the apparatus, in view of the further obstructions produced by the corners of said polygonal screen which generally was shaped in an hexagonal form. However, it has now been discovered that there is no reason whatsoever for maintaining the polygonal, particularly hexagonal shape of indented screens, because the said screens used in most of the prior art polishing machines for grains, do not have the previously believed performance and rather tend to produce, when the screen has few sides, heavy accumulation of grains in the corners of the screen, with the consequent disadvantage that this accumulation may produce.
The screen type machines of the prior art, on the other hand, generally use inadequately distributed indentations in the screens that interfere with the slots of the screen, thereby forming extremely sharp protuding edges that materially form sharp knives that, rather than polishing or husking the grain, cut the surface thereof and many times cut through the bodies of said grains with the consequent breakage and the obvious insatisfactory uniformity of the polishing or husking action achieved thereby.
Most of the above described drawbacks shown by all the prior art husking and polishing machines, particularly for rice, have been solved by the whitening and polishing machine of U.S. Pat. No. 3,960,068 to Felipe Salete, the same applicant of the instant application. Said patent discloses an air-swept polishing machine for rice which comprises a housing, a hollow rotor within said housing, feed means to admit grain into the housing, a screw conveyor at the lower part of said rotor for conveying the grains upwardly into the treating section of the machine which is arranged at the upper part of said rotor, a cylindrical indented screen in said treating section and a rotor having a pair of retractible knives to retain the movement of the grains at will, whereby the pressure applied by said screw conveyor upwardly of the machine, pushes the grain to be trapped by said rotor which spins the mass of grains against the action of the indented screen, thus rubbing the grains one to each other and against the walls of the rotor and the walls of the indented screen, to thereby polish the grains. The flour which is removed from the grains is entrained in a stream of air which is forced through the hollow rotor and outwardly thereof through suitable bores, in order to traverse the mass of spinning grains and the screen, and driving said flour from the treating chamber of the machine to be thereafter appropriately collected in an appropriate receptacle.
The treated grains are in turn pushed upwardly against a centrifugal extractor, which expels the same outwardly of the machine.
The above described machine of U.S. Pat. No. 3,960,068, however, does not solve the problem extant in practically all rice mills, namely, that if the rice is not properly husked in the husking section or machines, an additional husking operation and or unhusked grain removing operation is required in the husking stage, because the machine is unable to husk the unhusked grains received.
One other husking and polishing machine is the subject matter of U.S. Pat No. 4,292,890, to Felipe Salete, which solves the problems of the prior art machines including that of U.S. Pat. No. 3,960,068, by the incorporation of a new type of screen and rotor assembly, which comprises a cylindrical rotor having two particularly designed fluted knives tangentially arranged thereto, such that the grains are gradually pressed when trapped by each knife which is inclined outwardly of the periphery of the rotor contrary to the direction of movement of the same, and a screen supported by a specially designed screen holder, which comprises two semi-cylindrical screen members having appropriately distributed indentations to avoid sharp edges thereof, and which are attached and fastened to said screen holder at the edges of said semi-cylindrical screens, by means of the introduction of a pair of stationary knives, which are also fluted knives, said fluted knives having the flutes directed in such a manner that the flow of grains in the treatment chamber of the machine is forced downwardly while the stream of grain is pushed upwardly by the screw type conveyor which may be provided with abrasive material on the attacking face thereof, thus producing a higher compression of the grains, that are therefore rubbed with more energy and that therefore may be partially husked and polished and whitened in one single step.
This highly improved type of polishing and husking machine, however, still requires the provision of a husking stage before receiving the grain, because even with the highly improved characteristics of the screen and rotor assembly, it is unable to completely husk the grain and also polish the same in one single step.
It is therefore very well known that the workers in the art of husking and polishing cereal grains have long sought a machine that may be able to overcome the above described drawbacks and particularly a machine that may perform, in one single step, both full husking of the grains, as well as polishing thereof, in order to solve the very serious problems extant up to the present time in all prior art cereal mills, namely, that the husking machines generally must perform a husking operation with a very high efficiency and degree of husking, in order that the polishing machines may be capable of either only polishing the completely unhusked grains, or of only partially husking the still unhusked grain reaching the same, or requiring an unhusked grain removing stage, with the consequent increases in cost and efficiency of the mill.
It is to be pointed out that many machines of those described above are highly efficient for carrying out their husking and polishing actions, and that the only defective part thereof in order to accomplish the above mentioned goals, is the screen and rotor assembly, which up to the present time has not been designed in such a manner that it may, in conjunction with the other parts of the husking or polishing machines, accomplish the goal of completely husking the grain and at the same time rubbing the same gently in order to polish it.